6,6&#39;-methylenebis(2-styryl benzopyrylium salt)as sensitizers for use in electrophotographic light-sensitive materials

ABSTRACT

THERE ARE PROVIDED SENSITIVIZERS FOR USE IN AN ELECTROPHOTOGRAPHC LIGHT-SENSITIVE MATERIAL CONTAINING AN ORGANIC PHOTOCONDUCTOR. THE SENSITIZERS COMPRISES DERIVATIVES OF 6,6&#39;&#39;-METHYLENEBISZOPYRYLIUM SALTS.

June 4, 1974 SHOJI MARUYAMA ETAL 3,814,752

6,6"METHYLENEBIS[ZSTYRYL BENZOPYRYLIUM SALTS] AS SENSITIZERS FOR USE IN ELECTROPHOTOGRAPHIC LIG-HTSENSITIVE MATERIALS Filed June 5, 1972 2 Sheets-Sheet 1 FIG. I'

WAVE LENGTH (my) |00 Z lv z w 0 m 800 700 600 500 400 WAVE LENGTH (m 100 I I: Z L'. (D z m 0 800 700 600 500 400 WAVE LENGTH (mg) WAVE LENGTH(m,u) 4 2.53 45 6 75010 1152025 5100 I Z 9. 3 E5 LLIU) 8?: 1 i'E 4800 3200 2400 I800 |600|4OO I200 |OOO8006OO 400 WAVE NUMBER (cm") June 4, 1974 SHOJI MARUYAMA ETAL 3,814,752

{3,(1' -METHYLENEBISCZ-STYRYL BENZOPYRYLIUM SALTS AS SENSITIZERS FOR USE IN ELECTROPHOTOGRAPHIC LIGHT-SENSITIVE MATERIALS Filed June 5, 1972 2 Sheets-Sheet 2 WAVE LENGTH(m;L) 5

o zra 3 4 0 7 s 9 :0 2025 z 9 R LUV) mm 0 l l l l l l l l I l l V l l l l l l A l Q 4000 3200 2400 I800 I600 |400|200 |000 800 600 400 WAVE NUMBER (cm") FIG. 6

PERCENT TRANSMISSION I 500 I I I 600 I I I I 700 WAVE LENGTH (m FIG? PERCENT TRANSMISSION ("/o) 500 I I 600 700 WAVE LENGTH (mp) United States Patent Oflice- 3, 14,752 Patented June 4, 1974 US. Cl. 260-240 D 6 Claims ABSTRACT OF THE DISCLOSURE There are provided sensitizers for use in an electrophotographic light-sensitive material containing an organic photoconductor. The sensitizers comprise derivatives of 6,6-methylenebisbenzopyrylium salts.

BACKGROUND OF THE INVENTION It is well to use organic photoconductive materials such as polyvinylcarbazole instead of inorganic photoconductors such as photoconductive zinc oxide or selenium in electrophotographic light-sensitive materials. However, with organic photoconductors the sensitivity is low compared with inorganic photoconductors. Accordingly, in order to improve the sensitivity of organic photoconductors, it has been proposed to add certain coloring materials for sensitization. In this manner, the sensitivity of the organic photoconductive matter may be improved to a degree that it can be used in a practical manner. There is however still need for improvement.

It is an object of the present invention to provide sensitizers which will impart high sensitivity to organic photoconductors.

SUMMARY OF THE INVENTION The present invention relates to sensitizers for use in electrophotographic light-sensitive materials which contain organic photoconductors such as polyvinylcarbazole.

The sensitizers of the present invention are derivatives of 6,6-methylenebisbenzopyrylium salts having the following general formula:

6,6-methylenebis[2-(2',3',4'-trimethoxystyryl)-3 -phenylbenzopyrylium perchlorate] Compound No. 2

6, 6'-methylenebis [2- 4'-methoxynaphthylvinylene 3-phenylbenzopyrylium perchlorate] used as Compound No. 3

6,6-methylenebis[2-(3',4'-dimethoxystyryl)-3-phenylbenzopyrylium perchlorate] Compound No. 4

6, 6'-methylenebis[2-(p-methylstyry1) -3-phenylbenzopyrylium perchlorate] Compound No. 5

6,6-methylenebis [2- (2',4'-dimethoxystyryl) -3-phenylbenzopyrylium perchlorate] Compound No. 6

6,6'-methylenebis[2- (p-methoXystyryl)-3 -phenylbenzopyrylium perchlorate] Compound No. 7

6, 6-methylenebis [2- (p-ethoxystyryl) -3 -phenylbenzopyrylium perchlorate] Compound No. 8

6,6-methylenebis[2- (p-butoxystyryl)-3 -phenylbenzopyrylium perchlorate] Compound No. 9

w 6,6-methylenebis[2-(p-methoxystyryl)benzopyrylium perchlorate] Compound No. 10

6,6-methylenebis [2- (p-methoxystyryl) -3 -butylb enzopyrylium perchlorate] Compound No. 11

6,6-methylenebis[2-(p-ethoxystyryl)-3-octylbenzopyrylium perchlorate] Compound No. 12

6,6-methylenebis[2-(2',4'-dimethoxystyryl) -3-octylbenzopyrylium perchlorate] Compound No. 13

6,6-methylenebis[2-(p-methoxystyryl)-3-decylbenzopyrylium perchlorate] Compound No. 14

6,6-methylenebis [2-naphthylvinylene-3 -phenylbenzopyrylium perchlorate] Compound No. 15

6,6-methylenebis [2- (3 ',4'-diethoxystyryl) -3 -phenylb enzopyrylium perchlorate) Such derivatives of 6,6 methylenebisbenzopyrylium salts are used as sensitizers for an organic photoconductors such as polyvinylcarbazole or derivatives thereof. They are preferably used in an amount of 0.1 to 2.0% by weight based on the solid content, in a light-sensitive solution. Y

The elfects of the sensitizers of the present invention are illustrated in the following examples.

EXAMPLES 1-15 r so that the dried light-sensitivellayer, (coated layer) had a thickness of Sp. to 6p.

After each light-sensitive product was allowed to stand in a dark place for several days, it was negatively charged by means of conventional corona discharge of 6 kv. and exposed to white light in contact with an image Original while illuminating the surface of the light-sensitive layer at 20 lux.

In this manner, the optimum amount of exposure [lux-sec] required to obtain an exact reproduction of an original image on the light-sensitive layer was measured for each of Compounds No. 1 to No. 15.

Furthermore, by using the electrophotographic lightsensitive materials obtained above, the wave length of absorption maximum was measured by reflection method for each of Compounds No. 1 to No. 15.

The measured values are shown in the Table 1 below, and the curves of spectral sensitivity of the electrophotographic light-sensitive material sensitized with Compounds No. 1, No. 2 and No. 13 are shown in FIG. 1, FIG. 2 and FIG. 3 of the accompanying drawings, respectively.

EXAMPLES 16-30 Electrophotographic light-sensitive materials were obtained following the same procedures as that of Examples 1-15 except that chlorinated polyvinylcarbazole was employed as a substitute for brominated polyvinylcarbazole.

The electrophotographic light-sensitive materials yielded an exact reproduction of original images in the same manner as that of Examples 1-15 except that the lightsensitive materials were exposed to light for 2 seconds while illuminating the surface of the light-sensitive layer at 20 lux.

Derivatives of 6,6-methylenebisbenzopyrylium salts having general formula (I) are synthesized as follows:

Condensation of 5,5'-methylenebissalicylaldehyde of formula (II) with a ketone of general formula ('III) is carried out and to this reaction solution is added an aldehyde of general formula (IV) to carry out cyclic condensation.

C H O 2R2CHO OH; OH ZRICHBCOCHQ! As a condensingage'nt for the condensation "andth'e cyclic condensation, hydrochloricacid or hydrogen chlo ride may be used.

The reaction temperature of the condensation and the cyclic condensation is preferably between 0 C. and 5 C.

Introduction of an anion is effected as follows:

(1) After the cyclic condensation with aldehyde has'been' carried out in the presence of acid or salt having the desired anion, the reaction solution is poured into ether to crystallize.

(2) After cyclic condensation has been carried out, the reaction solution is poured into a cooled solution (concentration: 5-20%) containing acid or salt having a desired anion to crystallize.

Methods of producing derivatives of 6,6'-methylenebisbenzopyrylium salt are illustrated by the following Preparations No. 1 to No. 5.

Preparation No. 1

6,6-methylenebis[Z-(p-methoxystyryl) 3 phenylbenzopyrylium perchlorate] (Compound N0. 6 having the following formula) 2.5 g. of 5,5'-methylenebissalicylaldehyde was dissolved in 40 ml. of tetrahydrofuran and to this solution was added a solution containing 3 g. of benzyl methyl ketone in 20 ml. of formic acid. After having been well mixed, the solution was saturated with hydrogen chloride while cooling. The solution was allowed to stand in an ice box for 2 hours and then to this solution was added a solution containing 3 g. of p-methoxybenzaldehyde in 20 ml. of 90% formic acid. After this solution was saturated with hydrogen chloride while cooling and allowed to stand in an ice box for 2 days, the solution was poured into a 15% cooled aqueous solution of perchloric acid (HCI'O Crude crystals separated from the solution by allowing to stand for 30 minutes were filtered and recrystallized from 300 ml. of 90% acetic acid. 9.3 g. of crystals of the captioned compound (M.P. C- 187 C.) was thus obtained.

Percent of- Analysis (for ClOHasClzOlz) C H 01 Calculated 66. 21 4. 27 7. 88 Found- 66. 12 4. 18 8. 05

This compound showed wave length of absorption maximum (A at 576 111,11. and molecular extinction coefficient (e) of 1016x10 in dichloroethane.

Preparation No. 2

6,6 methylenebis[2 (4' methoxynaphthylvinylene)- 3-phenylbenzopyrylium perchlorate] (Compound No. 2 having the following formula) OCH solution conta i I Percent of Analysis roi- (261111015012) 1 o" 2 n '01 Calculated-.'..'.. 69.23 e25 7.08 Found;-;-. "--'Y69.18' e14 ass This compound showed wave length of absorption maximama... at 660 mpzand molecular extinction coefiicient (e) of 8.7) (10 in dichloroethane." Infrared absorption spectrum and transmission absorption spectrum of this compound are respectively shown'in FIG. 4 and FIG. 6 of the accompanying drawings.

Preparation No. 3

6,6-methylenebis [2 (p methoxystyryl) 3 decylbenzopyrylium-perchlorate] (Compound No. 13 having the following formula) v DoCI-Ia 7 2 g. of 5,5-'-methylenebissalicylaldehyde was dissolved in 50 ml. of ethyl alcohol and to'this solution was added a solution containing 7.6 g. of methyl undecyl ketone in 40 ml. of 90%% acetic acid. After having been well mixed, the solution was saturated with hydrogen chloride while cooling. The solution was allowed to stand in an ice box for 4 days and then to this solution was added a solution containing 5.2 g. of p-methoxybenzaldehyde in 20 ml. of 90% formic acid. This solution was saturated with hydrogen chloride, and thereafter the same procedure as that of Preparation No. 1 was repeated. 13.5 g. of crystals of the captioned compound (M.P. 173 C.- 174 %C.) was thus obtained.

Percent of- Analysis (for C5'IH70C11012) C H 01 Calculated 62. 40 6. 38 6. 38 Found 62. 38 6. 42 6. 35

This compound showed wave length of absorption maximum (A at 559 my and molecular extinction coefiicient (e) of 8.79X10 in dichloroethane.

Preparation No. 4

6,6 methylenebis[2 (2',3',4' trimethoxystyryl)-3- phenylbenzopyrylium perchlorate] (Compound No. 1 having the following formula) H 00 OCH;

2.5 g. of 5,5-methylenebissalicylaldehyde was dissolved in 40 ml. of tetrahydrofuran and to this solution was added a solution containing 3 g. of benzyl methyl ketone in 20 ml. of 90% acetic acid. After having been well mixed, the solution was saturated with hydrogen chloride while cooling. The solution was allowed to stand in an ice box for 2 hours and then to this solution was added a solution containing 4 g. of 2,3,4-trimethoxybenzaldehyde in 30 ml. of 90% acetic acid. This solution was saturated with hydrogen chloride while cooling and thereafter the same procedure as that of Preparation No. l was repeated 8.0g. of crystals ofithe captioned compound (M.P. 223 C.'225- C.) was'thus obtained.

Percent ofmaximum x at 607 my and molecular extinction coefiicient (e) of 7.4x 10 in dichloroethane.

Preparation No. 5

6,6'-methylenebis[2 (2',4' dimethoxystyry1)-3-octylbenzopyrylium perchlorate] (Compound No. 12 having the following formula) zlzC a 2 2.6 g. of 5,5'-methylenebissalicylaldehyde was dissolved in 50 ml. of tetrahydrofuran and to this solution Was added a solution containing 3.4 g. of methyl nonyl ketone in 20 ml. of formic acid. After having been well mixed, the solution was saturated with hydrogen chloride while cooling. The solution was allowed to stand in an ice box for 3 days and then to this solution was added a solution containing 3.2 g. of 2,4-dimethoxybenzaldehyde in 10 ml. of 90% formic acid. This solution was saturated with hydrogen chloride while cooling and thereafter the same procedure as that of Preparation No. 1 was repeated. 7.5 g. of crystals of the captioned compound (M.P. 200 C.;202 C.) was thus obtained.

Percent of- Analysis (for CaaHzsClzOu) C H 01 Calculated 64. 57 6. 45 6. 84 Found 64. 38 6. 51 6. 90

6,6'-methylenebis[Z-naphthylvinylene-3-phenylbenzopyrylium perchlorate] (Compound No. 14)

o\ oH=oH (M.P. 218 C.-220 C.)

6,6'-methylenebis[2-(p-methoxystyryl)-3-butylbenzopyrylium perchlorate] (Compound No. 10)

OCHa

on, 421 j (M.P.249 C.250 C.) I H I 6,6-methyle'nebis[2-( g-ethoxystyryl.)r3 phenylbenzq 1; pyrylium perchlorate] (Compound No.7)

0+ l cn=ono 02115 CH: 'CIOF (M.P. 250 C'251 C.)

In the above-mentioned Examples and Preparations, benzopyrylium salts having C10 as an anion have been shown. Benzopyrylium salts having BF;- or AuCl; as an anion can be obtained by using an aqueous solution of sodium tetrafluoroborate (NaBF or chloroauric acid (HAuCl instead of an aqueous solution of perchloric acid (H010 We claim:

1. A sensitizer for use in an electrophotographic lightsensitive material having the formula (I):

\ CH=CHRg CH1 A rivative isj- 6;6' methvlenebisn (4Gmethoxynaphthyii '4. A sensitize: afbording'tofclaim'lfwheiiein rivativ'e" is 6,6 "'methy1enebis'[2 (p"-methoxystyryl)-3'- decylbenzopyryliumperchlorate a 5. A sensitizer according? to; claim .IWherein thevderi-var tive is 6,6 methylenebis[2-(2Z3i,4f-trimethoxystyryl)& 3-phenylbenzopyrylium perchlorate,

6. A sensitizer according to elaim l yvherein the deriva-v tive is 6,6 methy1enebis[2 =.(,2,, -,dimethoxystyryl)-3- octylbenzopyryliumperchlorate Y 

